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Cardiovascular > Understanding ECGs > Flashcards

Understanding ECGs Flashcards

1
Q

what type of activity does an ECG show?

A 
electrical activity
(not mechanical ie wont see valves closing etc)
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2
Q

what is the name of the recording of potential differences in the heart?

A

electrocardiogram

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3
Q

what is the name for the separation of charge one after the other?
(depolarisation and then hyperpolarisation)

A

dipole

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4
Q

what do electrodes record?

A

the difference in potential between two points

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5
Q

when will the net potential measured by the electrodes be 0mV?

A

when the lead (ie imaginary line between 2 electrodes) is perpendicular to the dipole

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6
Q

what is the leading charge and what is the lagging charge of the cardiac dipole?

A

leading charge: positive

lagging chard: negative

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7
Q

what limb lead is the most parallel to the cardiac dipole?

A

lead II

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8
Q

how does a lead look at the moving charge?

A

looks from the positive electrode to the wave coming towards it from the negative electrode

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9
Q

what direction does the depolarisation have to move in order for an upwards deflection?

A

depolarisation needs to be moving towards positive electrode

ie positive electrode is looking at wave coming towards it

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10
Q

what are PR, ST and TP intervals flat on an ECG?

A

because there is no moving wave

ie no change in potential at that time

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11
Q

how are augmented limb leads formed?

A

1 of the limb electrodes acts as the positive recording electrode and the other 2 are coupled together as teh negative reference electrode

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12
Q

what limb electrodes make up aVR?

A

positive electrode: RA

negative electrode: LA+LL

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13
Q

what limb electrodes makes up aVL?

A

positive electrode: LA

negative electrode: LL+RA

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14
Q

what limb electrodes make up aVF?

A

positive electrode: LL

negative electrode: LA+RA

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15
Q

why is the aVR recordings downwardly deflecting?

A

because the wave is manly moving away from the positive electrode

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16
Q

why is the limb lead II particularly good for looking at electrical activity?

A

because the wave is parallel to the lead axis and so has a great net potential difference so has well resolved waves

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17
Q

why is limb III not too good for looking at electrical activity?

A

because the wave is almost perpendicular to the lead axis so has a very small net potential difference so has poorly resolved waves

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18
Q

how many chest electrodes are there?

A

6

19
Q

where is chest electrode 1 and what lead does it form?

A

1: 4th intercostal space, R of sternum

lead = V1

20
Q

where is chest electrode 2 and what lead does it form?

A

2: 4th intercostal space, L of sternum

lead = V2

21
Q

where is the chest electrode 3 and what lead does it form?

A

3: between 2 and 4

lead = V3

22
Q

where is the chest electrode 4 and what lead does it form?

A

4: 5th intercostal space midclavicular line

lead = V4

23
Q

where is the chest electrode 5 and what lead does it form?

A

5: 5th intercostal space anterior axillary line

lead = V5

24
Q

where is the chest electrode 6 and what lead does it form?

A

6: 5th intercostal space mid-axillary line

lead = V6

25
Q

what gives the negative reference electrode for the chest leads?

A

all 3 limb leads combines

roughly the ecentre of the heart

26
Q

what happens to the limb leads if chest leads arent working?

A

nothing

27
Q

what happens to the chest leads if the limb leads aren’t working?

A

chest leads don’t work either

28
Q

what plane do the limb leads show?

A

frontal plane

29
Q

what plane do the chest leads show?

A

horizontal plane

30
Q

how long should the P wave be?

A

0.08- 0.10 seconds

between 2/3 small boxes

31
Q

how long should the PR interval be?

A

0.12 - 0.2s

between 3/5 small boxes

32
Q

what should the normal callibration of ECG be?

A

paper speed = 25mm/sec

10mm amplitude = 1mV

33
Q

what is one small square on ECG paper?

A

1mm, 0.04s

34
Q

what is one big square on ECG paper?

A

5mm, 0.2s

35
Q

how many big squares and little squares are there per second?

A

5 big squares per second

25 small squares per second

36
Q

how do you figure out the heart rate?

A

300/

no.of big squares between QRS complexes

37
Q

what is the ECG rhythm strip?

A

a prolonged recording of lead 2 which allows you to detect rhythm distrubances

38
Q

what is the step by step approach to analysing an ECG rhythm strip?

A
  1. clarify patient
  2. date/time of ECG
  3. check calibration of the machine
  4. is electrical activity present?
  5. is the rhythm irregular or irregular?
  6. what is the heart rate?
  7. are there P waves present?
  8. is the PR interval normal?
  9. is each p wave followed by a QRS complex
  10. is QRS duration normal
  11. look for individual leads for changes
39
Q

how would you tell if the cardiac rhythm is regular or irregular from a rhythm strip?

A

if rhythm is regular, QRS complexes occur at regular intervals

40
Q

how can you calculate the heart rate from a rhythm strip if the rhythm is irregular?

A

count number of QRS complexes within 30 big squares and times that by 10

41
Q

what can it mean if the PR interval is too long?

A

problem with AV conduction

42
Q

what does it mean if each P wave is followed by a QRS complex?

A

sinus rhythm

43
Q

how long should a QRS complex be?

A

less than 0.10 seconds

less than 3 small boxes

Cardiovascular (12 decks)

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